The field of the invention is polyamide powders.
The state of the prior art of producing and using polyamide powders and the polyamide raw materials may be ascertained by reference to U.S. Pat. Nos. 2,698,966; 2,742,440; and 2,975,126 of Louis L. Stott; U.S. Pat. No. 3,203,822 of Junker et al; U.S. Pat. Nos. 3,410,832 of Griehl et al; 3,299,009 of Stephen D. Bruck; East German Pat. No. 8027 of Hermann Wenderoth, dated May 27, 1953 and the Kirk-Othmer "Encyclopedia of Chemical Technology," 2nd Ed., Vol. 16 (1968), under the section "Polyamide (Plastics)," pages 88-105, particularly page 92- Polylauryllactam (nylon-12), and polyundecanamide (nylon-11), page 101 Solution Processes and Powder Processing, pages 101-102, the disclosures of which are incorporated herein.
U.S. Pat. No. 2,698,966 discloses physical mixtures of different types of nylon powders produced by dissolving the nylon in organic solvents and precipitating the powdered particles. In Example 14 of U.S. Pat. No. 2,742,440, the solution of epsilon caprolactam polymer in alcohol-water solution and its precipitation as a powder is disclosed. The dispersion of Teflon powder in a solution of epsilon caprolactam polymer and the coprecipitation of the powders is disclosed in U.S. Pat. No. 2,975,128.
The flame spraying and fluidized bed coating of nylon on a metal base is disclosed in U.S. Pat. No. 3,203,822. U.S. Pat. No. 3,299,009 discloses the n-methoxymethylation of nylons, and U.S. Pat. No. 3,410,832 discloses the preparation of polymers and copolymers of lauryllactam.
It is old in the art to prepare polyamide powders by precipitating polyamides from solutions as disclosed in German Pat. Application S 2805 39b-22/04 laid open to inspection Oct. 5, 1951 and corresponding to British Pat. No. 688,771 and French Pat. No. 989,062. It is also known to use dimethyl formamide as a solvent as disclosed in East German Pat. No. 8027. Conventionally, the granular polyamides are subjected to extraction prior to further processing, in order to remove the monomerous and low molecular ingredients.